The arrangements disclosed in the prior art (DE 10 2010 038 136 A1 and DE 10 2008 035 498 A1) contain a tire module comprising a device for measuring and/or monitoring the air pressure in the tire, having a transmitter for transmitting radio signals which contain information on the air pressure in the tire, a mechanical-electrical transducer which converts changes in the shape of the transducer caused by the rolling tire into electrical energy, and has an accumulator for the electrical energy. In the known tire module, the mechanical-electrical transducer comprises a bendable piezoelectric element, which is located on a thin, flexible metal disk as the carrier. Document DE 10 2010 038 136 A1 discloses a capacitor as the accumulator for the electrical energy.
The tire module is completed by a casting compound, in which components of the tire module are entirely or partially embedded. The tire module is inserted in a cover, which is made of an elastomeric material and has a flange, which forms the edge of the interior space of the cover, extends outwardly away from the tire module and completely encloses an opening to the interior space of the cover. In the exemplary embodiment disclosed in DE 10 2010 038 136 A1, the cover and the tire module are substantially circular as viewed from above and the interior space of the cover is substantially circularly cylindrical. The outer dimensions of the tire module, which includes the casting compound, and the inner dimensions of the cover are matched to one another, wherein the tire module—as long as the cover is not mounted on the inner side of the tire—preferably protrudes slightly out of the cover in a downward direction such that the cover is under mechanical preload after said cover has been fastened via the flange thereof on the inner side of the tire. This results in a tight coupling of the mechanical-electrical transducer to the inner side of the tire.
The connection of the cover flange to the inner side of the tire can take place via adhesive bonding or vulcanization.
In the known tire module, the mechanical-electrical transducer along with the carrier thereof is disposed directly on the inner side of the tire such that deformations of the inner side of the tire are transmitted to the mechanical-electrical transducer, which converts the changes in shape occurring thereon into electrical energy, which is stored in the tire module for the operation of the measurement and transmission devices. These changes in shape are periodically transmitted to the mechanical-electrical transducer, when the tire is rolling, every time the tire module enters the shuffle thereof and re-emerges from the shuffle. The shuffle is that part of the tire that has momentary contact with the road.
Experience has shown that the efficiency of the known mechanical-electrical transducer can decrease as operating time increases. This is disadvantageous because the electrical energy available in the accumulator decreases as a result and the time intervals between measurement processes and between transmission processes become longer because the energy required for more frequent measurement and transmission processes is no longer available. This is disadvantageous, in turn, because continuous, automatic tire pressure monitoring is important for the safety of a vehicle and is that much better the more frequently the tire pressure monitoring can be carried out and the more frequently the result can be wirelessly transmitted.
The problem addressed by present invention is that of preventing or at least slowing a decrease in the efficiency of the mechanical-electrical transducer, as far as possible, in an arrangement of the initially mentioned type.